Human mesenchymal stromal cells response to biomimetic octacalcium phosphate containing strontium.

The incorporation of bioinorganics into synthetic biomaterials is a promising approach to improve the biological performance of bone graft substitutes, while still retaining their synthetic nature. Among these bioinorganics, strontium ions (Sr2+) have reported enhanced bone formation, and a reduced risk of bone fractures. While previous results have been encouraging, more detailed studies are needed to further develop specific applications. This study demonstrates the effects of Sr2+ on the osteogenic differentiation of human mesenchymal stromal cells (hMSCs) when introduced as either a dissolved salt, or incorporated into biomimetic calcium phosphate (CaP) coatings. Upon attachment, hMSCs seeded in the presence of higher Sr2+ concentrations presented with a more elongated shape as compared to the controls without Sr2+. Both Sr2+ as a dissolved salt in the medium, or incorporated into CaP coatings, positively influenced hMSC alkaline phosphatase (ALP) activity in a dose-dependent manner. At the mRNA level, the expression of osteogenic markers ALP, bone sialoprotein, bone morphogenetic protein 2, osteopontin, and osteoclacin were increased in the presence of Sr2+, independent of the delivery method. Overall, this study demonstrates the positive effects of strontium on the osteogenic differentiation of human MSCs, and supports the use of strontium-incorporated CaPs for bone regeneration applications. (c) 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1946-1960, 2016.